Su Yahan, Yang Huan, Wu Yushan, Gong Wanzhuo, Gul Hina, Yan Yanhong, Yang Wenyu
College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China.
Key Laboratory of Crop Eco-Physiology and Farming System in Southwest of China, Sichuan Engineering Research Center for Crop Strip Intercropping System, Chengdu 611130, China.
Plants (Basel). 2023 Jun 15;12(12):2324. doi: 10.3390/plants12122324.
Soybean in relay intercropping is initially exposed to a shade environment, followed by exposure to full sunlight after the harvesting of primary crops, e.g., maize. Therefore, soybean's ability to acclimate to this changing light environment determines its growth and yield formation. However, the changes in soybean photosynthesis under such light alternations in relay intercropping are poorly understood. This study compared the photosynthetic acclimation of two soybean varieties with contrasting shade tolerance, i.e., (shade-tolerant) and (shade-intolerant). The two soybean genotypes were grown in a greenhouse under full sunlight (HL) and 40% full sunlight (LL) conditions. Subsequently, after the fifth compound leaf expanded, half of the LL plants were transferred to a high-sunlight environment (LL-HL). Morphological traits were measured at 0 and 10 days, while chlorophyll content, gas exchange characteristics and chlorophyll fluorescence were assayed at 0, 2, 4, 7 and 10 days after transfer to an HL environment (LL-HL). Shade-intolerant showed photoinhibition 10 days after transfer, and the net photosynthetic rate () did not completely recover to that under a high light level. On the day of transfer, the shade-intolerant variety, , exhibited a decrease in net photosynthetic rate (), stomatal conductance () and transpiration rate () in the low-light (LL) and low-light-to-high-light (LL-HL) treatments. Additionally, intercellular CO concentration () increased in low light, suggesting that non-stomatal factors were the primary limitations to photosynthesis in following the transfer. In contrast, the shade-tolerant variety, , displayed a greater increase in 7 days after transfer, with no difference observed between the HL and LL-HL treatments. Ten days after transfer, the shade-tolerant exhibited 24.1%, 10.9% and 20.9% higher biomass, leaf area and stem diameter than the intolerant . These findings suggest that possesses a higher capacity to adapt to variations in light conditions, making it a potential candidate for variety selection in intercropping systems.
套种的大豆最初处于遮荫环境，在主作物（如玉米）收获后则会暴露在充足的阳光下。因此，大豆适应这种不断变化的光照环境的能力决定了其生长和产量形成。然而，对于套种中这种光照交替下大豆光合作用的变化，人们了解甚少。本研究比较了两个耐荫性不同的大豆品种的光合适应性，即（耐荫）和（不耐荫）。这两个大豆基因型在温室中于全光照（HL）和40%全光照（LL）条件下生长。随后，在第五片复叶展开后，将一半的LL植株转移到高光环境（LL-HL）。在转移到HL环境（LL-HL）后的第0天和第10天测量形态特征，在转移后的第0、2、4、7和10天测定叶绿素含量、气体交换特性和叶绿素荧光。不耐荫的在转移10天后表现出光抑制，净光合速率（）未完全恢复到高光水平下的速率。在转移当天，不耐荫品种在低光照（LL）和低光照转高光照（LL-HL）处理中，净光合速率（）、气孔导度（）和蒸腾速率（）均下降。此外，低光照下细胞间CO浓度（）升高，表明转移后，非气孔因素是光合作用的主要限制因素。相比之下，耐荫品种在转移7天后的增加幅度更大，HL和LL-HL处理之间未观察到差异。转移10天后，耐荫的生物量、叶面积和茎直径分别比不耐荫的高24.1%、10.9%和20.9%。这些结果表明，具有更高的适应光照条件变化的能力，使其成为间作系统中品种选择的潜在候选品种。
